Fatigue Impact Scale (FIS)

The FIS was used to assess the impact of fatigue on everyday life activities. This scale includes 40 items in three subgroups: (1) Cognitive, which contains 10 items and focuses on the concentration, memory, thinking and organization of thoughts; (2) Physical, which includes 10 items and reflects motivation, endeavor, tolerance and coordination; and (3) Social, which includes 20 items and describes the effects of fatigue on isolation, emotion, stress, and communication. The intraclass correlation (ICC) values for inter-rater reliability in the physical, cognitive, and social subgroups of FIS and the whole questionnaire were 0.89, 0.86, 0.95 and 0.98, and for test–retest reliability were 0.86, 0.78, 0.92 and 0.93, respectively. The above findings taken together with a Cronbach α of 0.95 indicate a high reliability for the FIS Persian version.³¹